(PHP 5 >= 5.1.0, PHP 7, PHP 8)
DOMXPath::evaluate — Evaluates the given XPath expression and returns a typed result if possible
$expression, ?DOMNode $contextNode = null, bool $registerNodeNS = true): mixed
Executes the given XPath expression and returns
a typed result if possible.
expressionThe XPath expression to execute.
contextNode
The optional contextNode can be specified for
doing relative XPath queries. By default, the queries are relative to
the root element.
registerNodeNS
The optional registerNodeNS can be specified to
disable automatic registration of the context node.
Returns a typed result if possible or a DOMNodeList
containing all nodes matching the given XPath expression.
If the expression is malformed or the
contextNode is invalid,
DOMXPath::evaluate() returns false.
示例 #1 Getting the count of all the english books
<?php
$doc = new DOMDocument;
$doc->load('book.xml');
$xpath = new DOMXPath($doc);
$tbody = $doc->getElementsByTagName('tbody')->item(0);
// our query is relative to the tbody node
$query = 'count(row/entry[. = "en"])';
$entries = $xpath->evaluate($query, $tbody);
echo "There are $entries english books\n";
?>
以上例程會(huì )輸出：
There are 2 english books